1. Field of the Invention
The present invention relates to a push button switch. Typically, such a switch might include a small-sized casing which is square in plan and formed into, for example, a rectangular parallelpiped having dimensions of 6 mm in length, 6 mm in width and 4 mm in height. It would generally have a push button, a diaphragm type movable contact, fixed contacts, and terminals connected to a circuit for the fixed contacts, all arranged in the casing. When a push button projecting from the cover of the casing is pushed down, the movable contact is depressed to contact the fixed contacts to turn the switch on.
2. Description of the Prior Art
A conventional push button switch is shown in FIG. 8. It includes a casing 1 consisting of a small generally square body 1a made of an insulating plastic material, a lid or cover 1b made of a thin metal sheet, and also a push button 2, a diaphragm type movable contact 3, fixed contacts 4 and terminals 4a connected to a circuit of the fixed contacts 4 all arranged in the casing 1. The push button 2 is made of an insulating plastic material and is so arranged that the upper portion of a button section 2a of the push button 2 projects from the cover 1b through an aperture 5. The movable contact 3 includes a diaphragm made of a metal sheet, a conductive rubber material, a conductive plastics material or the like, and a conductive section formed of a conductive coating material on the inner surface of the diaphragm to prove at least the inner surface with conductivity. The fixed contacts 4 and terminals 4a are formed by embedding metal sheet in the casing body 1a by inserting moulding during forming of the casing body 1a. Alternatively, they may at least in part comprise a printed board.
The push button switch so constructed is used in electrical and electronic appliances such as video units, televisions and the like in numbers as high as tens of millions per month.
The manufacture of this conventional push button switch will now be described, assuming that the fixed contacts 4 and terminals 4a are formed by insert moulding.
The casing body 1a, provided with the fixed contacts 4 and terminals 4a, and the push button 2 are respectively made by moulding a plastic material. The cover 1b and diaphragm type movable contact 3 are made from a metal sheet by pressing. The movable contact 3 and push button 2 are then inserted into the casing body 1a and the cover 1b is integrally mounted on the casing body 1a by suitable means such as fitting, caulking or the like.
As will be understood from the foregoing, the conventional push button switch requires that the casing body 1a, push button 2, cover 1b, and the movable contact 3 are made separately from one another, so that manufacturing the push button switch tends to be highly complicated. Also, the manufacture requires integration of the separately made components for assembling of the switch, resulting in further difficulties and complications.
Thus, the conventional push button switch requires four independant components, namely, the casing body 1a provided with the fixed contacts 4 and the terminals 4a in this case, the cover 1b, the push button 2, and the diaphragm type movable contact 3. The components are each required to be formed by moulding or pressing. It will be appreciated that a decrease in the number of parts or a decrease in the number of moulds and moulding or pressing operations would be highly desirable because it would necessarily lead to an increase in the efficiency of the manufacturing process and a reduction in manufacturing costs.
The formation of a container and its cover according to conventional plastic moulding techniques is generally carried out by integrally forming the container and cover together while interconnecting both through a thin-wall section between them, the thin-wall section providing a hinge in the finished product.